The maintenance and repair of nuclear steam supply system steam generators often involves operations such as machining (EDM), removing, plugging, sleeving, rolling and welding of portions of the steam generator U-shaped tubes from the primary side of the tubesheet. These operations typically expose one or more operators to radiation in a manner which may be hazardous to their health.
To conduct maintenance and repair operations in a steam generator with a minimum of ionizing radiation exposure to the operators, post with cantilevered arm manipulators have been used to move end effectors (tools and sensors) into operative position under the tubesheet in the primary chamber. The manipulators and tools are put in and removed from the steam generators by the operators and the manipulators are used to move the tools during operations on the tubes. Some systems have been devised to minimize the time operators must be physically in the steam generators. These, typically, permit attaching and detaching the tools on the manipulating arm from a platform adjacent the access opening of the steam generator and using the arm to move the tool to and from the working position on the primary side of the tubesheet.
In the past, the most common method of attaching and detaching the tools has been by mounting two mating "dovetailed" pieces, one mechanically fastened on the end and one fastened on the tool, with a manually operated spring-biased lock to hold them together.